1. Field of the Invention
This invention relates generally to a process of forming a nano-pitted substrate that serves both as patterns to grow nanostructured materials and as current collectors for the nanostructured material that has been grown thereupon.
2. Description of the Related Art
The potential of nanotechnology to provide new technological breakthroughs is the object of much current attention. Nanostructured materials have the potential for enhanced properties and efficiency improvements in virtually every area of science and technology through enhanced surface areas and quantum-scale reactions.
The process of nanoscale or microscale deposition of particles by a sputtering process is the ejection of particles from a condensed-matter target due to the impingement of energetic projectile particles onto a substrate having a plurality of holes or pores that range in diameter between ten (10) micrometers to one (1) nanometer (nm). Operatively, the source of coating material, referred to as the target or substrate, is mounted opposite to the sample, in this case a porous substrate in a vacuum chamber. The most common method of generating ion bombardment is to backfill the evacuated chamber with a continual flow of gas and establishing a glow discharge, indicating that ionization is occurring. A negative potential applied to the target causes it to be bombarded with positive-ions while the substrate is kept grounded. Impingement of the positive-ion projectile results in ejection of target atoms or molecules and their deposition on the substrate.
One of the most useful characteristics of the sputtering process is its universality: virtually any material is a coating candidate. Sputtering systems assume an almost unlimited variety of configurations, depending on the desired application. DC discharge methods are often used for sputtering metals, while an RF potential is used for less conductive materials. Ion-beam sources can also be used. Targets may be elements, alloys, or compounds, in either doped or un-doped forms, and can be employed simultaneously or sequentially. The substrate may be electrically biased so that it too undergoes ion bombardment. A reactive gas may be used to introduce one of the coating constituents into the chamber, i.e. oxygen to combine with sputtered tin to form tin oxide (reactive sputtering).
A nanostructure fabricated by RF sputtering of barium strontium titanate (BST) on porous alumina substrates suggests that the sputtered material does not penetrate into pores, but rather preferentially gathers along the continuous circular edge of pore openings. These types of sputtered metal structure or “antidots” are not partially or complete capped, are not layered, are formed only from metals, and are not used to assemble any type device.
Nanotubes and other nanostructures may be formed as large arrays, and in this form are often referred to as nanoporous or mesoporous structures. “Meso-porous” tin oxide structures have been created using surfactant templating techniques. The resultant material, however, consists of material containing irregular nanopores averaging about two (2) nm in size, without long-range order. These nanoporous or mesoporus structures cannot be formed in large arrays of tunable pore sizes, which develop wall height as well as porosity, and also cannot be partially or completely capped to form a nanobasket structure.
The assembly of individual nanostructured components into a three-dimensional battery system has been proposed as the means to promote ion diffusion in electrode materials by substantially increasing the effective electrode surface area to improve energy per unit area characteristics and promote a high rate charge/discharge capacity. Such features should enhance general battery performance, but they are of particular importance for thin film batteries and nanobatteries able to power proposed micro and nano electromechanical systems (MEMS and NEMS). Recent work on three-dimensional architectures for improved performance includes rods or “posts” connected to a substrate, graphite meshes and films of cathode, electrolyte and anode materials lining microchannels in an inert substrate.
Moreover, nanostructured electrode materials have been shown to have enhanced electrode properties such as faster charging/discharging properties and higher available capacities. These electrodes have the potential to be placed in battery configurations, especially where thin film construction is used. The two current collectors which are conductive material in the battery that collect electrons (on the anode side) or disburse electrons (on the cathode side) are present. It is the current collectors that serve to make contact between the devices that batteries power on one side and the two electrodes of the battery on their opposite sides.
Prior nanostructured electrode materials were grown from a substrate that is an insulating material, such as alumina. As the electrode material is grown on the substrate, the structure of the substrate is maintained as the sputter coated layer becomes thicker. However, the growth substrate, being an insulator, cannot serve as a current collector. As such, in order to construct a battery, the delicate nanostructured electrode must be removed from the substrate and a current collector must then be connected to the delicate nanostructured electrode (sometimes the layer is only 500 nm thick) without damaging it. This is one of the important considerations for application of nanoscale materials and engineering into what will result in a “real world” sized product is how to connect the nanoscale aspects of the system to the macroscale.
It is therefore desirable to provide a nanopatterned substrate that serves as both a current collector and template for nanostructured electrode growth.
It is further desirable to provide a process of constructing of a nanostructured current collector that serves as both a current collector and as a substrate to grow nanostructured electrode materials.
It is still further desirable to provide a nanopatterned substrate that serves as both a current collector and template for nanostructured electrode growth that bridges the gap between the nanoscale environment and the macroscale of commercial batteries.
It is yet further desirable to provide a nanopatterned substrate that serves as both a current collector and template for nanostructured electrode growth for thin film batteries and nanobatteries, which would be able to power proposed micro- and nano-electromechanical systems (MEMS and NEMS), or used in massive arrays in place of conventional batteries.
It is still yet further desirable to provide a process for manufacturing thin film batteries and nanobatteries using short, capped nanotubes, i.e., nanobaskets, electrochemical deposited directly on a nanopatterned substrate, which serves as both a current collector and the nanobasket growth template.
It is further desirable to provide a thin film battery or nanobattery constructed on a nano-pitted metal that serves as the growth substrate and the current collector for the electrode.
It is further desirable to provide a process of fabricating a thin film battery or nanobattery in which the electrode material does not have to be removed from its growth substrate.